| With the development of communication and space technology, circularly polarized antennas have great advantage and make the important role in wireless communication field. Linear polarized wave will have the polarization deflection effect in transmission and bring energy loss, but the polarized wave will return when it meet an obstacle, because of the polarization isolation between direct wave and reflect wave, it also has outstanding anti-jamming and anti-misty rain ability. In military and civilian field, the circularly polarized antenna has been widely used already.In the paper, the design theory and implementation method of the circularly polarized antenna have been researched, and the content can be mainly divided into two parts, which is plane spiral antenna and microstrip circularly polarized antenna. The first part is about one carinal cavity Archimedes spiral antenna, which has the work frequency of 1.4GHz to 2.5GHz, the diameter of 104cm and the height of 50cm. In the termination of the antenna, one shorted flake with the characteristic impedance of 140 Ohm is added as the matched load; meanwhile, one metal ring is laid on the surface of medium, in this way antenna axial ratio characteristics can be improved a lot. The second part in based on microstrip antenna theory, the author designed a circularly polarized patch antenna with double-fed finger load, analyzed the effect of antenna capability which is made by finger load. According to EM simulation and optimization with Ansoft HFSS, we can conclude that compared with traditional double-fed antenna, in the same Theta, this kind of antenna has a better axial ratio and radiation pattern. |
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